was customary. But normally the humans hid in the mushroom-forests, sheltered by the toadstools which now grew to three man-heights. They denned in small openings in the tangled mass of parasitic growths which flourished in such thickets. But this last night they had camped in the open. They had no proper habitations of their own. Caves would have been desirable, but insects made use of caves, and the descendants of insects introduced untold centuries before had shared in the size-increase of paramecium and yeasts and the few true plants which had been able to hold their own. Mining-wasps were two yards long, and bumble-bees were nearly as huge, and there were other armored monstrosities which also preferred caves for their own purposes. And of course the humans could not build habitations, because anything men built to serve the purpose of a cave would instantly be preempted by creatures who would automatically destroy any previous occupants.

The humans had no fixed dens at any time. Now they had not even shelter. They lacked other things, also. They had no tools save salvaged scraps of insect-armor—great sawtoothed mandibles or razor-pointed leg-shells—which they used to pry apart the edible fungi on which they lived, or to get at the morsels of meat left behind when the brainless lords of this planet devoured each other. They had not even any useful knowledge, except desperately accurate special knowledge of the manners and customs of the insects they could not defy. And on this special morning they concluded that they were doomed. They were going to be killed. They stood shivering in the open, waiting for it to happen.

It was not exactly news. They had had warning days ago, but they could do nothing about it. Their home valley, to be sure, would have made any civilized human being shudder merely to look at it, but they had considered it almost paradise. It was many miles long, and a fair number wide, and a stream ran down its middle. At the lower end of the valley there was a vast swamp, from which at nightfall the thunderously deep-bass croaking of giant frogs could be heard. But that swamp had kept out the more terrifying creatures of that world. The thirty-foot centipedes could not cross it or did not choose to. The mastodon-sized tarantulas which ravaged so much of the planet would not cross it save in pursuit of prey. So the valley was nearly a haven of safety.

True, there was one clotho spider in its ogre's castle nearby, and there was a labyrinth spider in a minor valley which nobody had ever ventured into, and there were some—not many—praying-mantises as tall as giraffes. They wandered terribly here and there. But most members of insect life here were absorbed in their own affairs and ignored the humans. There was an ant-city, whose foot-long warriors competed with the humans as scavengers. There were the bees, trying to eke out a livelihood from the great, cruciform flowers of the giant cabbage-plants and the milkweeds when water-lilies in the swamps did not bear their four-foot blooms. Wasps sought their own prey. Flies were consumers of corruption, but even the flies two feet in length would shy away from a man who waved his arms at it. So this valley had seemed to these people to be a truly admirable place.

But a fiend had entered it. As the gray light grew stronger the shivering folk looked terrifiedly about them. There were only twenty of the people now. Two weeks before there had been thirty. In a matter of days or less, there would be none. Because the valley had been invaded by a great gray furry spider!

There was a stirring, not far from where the man-folk trembled. Small, inquisitive antennae popped into view among a mass of large-sized pebbles. There was a violent stirring, and gravel disappeared. Small black things thrust upward into view and scurried anxiously about. They returned to the spot from which they had emerged. They were ants, opening the shaft of their city after scouting for danger outside. They scratched and pulled and tugged at the plug of stones. They opened the ant-city's artery of commerce. Strings of small black things came pouring out. They averaged a foot in length, and they marched off in groups upon their divers errands. Presently a group of huge-jawed soldier-ants appeared, picking their way stolidly out of the opening. They waited stupidly for the workers they were to guard. The workers came, each carrying a faintly greenish blob of living matter. The caravan moved off. The humans knew exactly what it was. The green blobs were aphids—plant lice: ant-cows—small creatures sheltered and guarded by the ants and daily carried to nearby vegetation to feed upon its sap and yield inestimable honeydew.

Something reared up two hundred yards away, where the thin mist that lay everywhere just barely began to fade all colorings before it dimmed all outlines. The object was slender. It had a curiously humanlike head. It held out horrible sawtoothed arms in a gesture as of benediction—which was purest mockery. Something smaller was drawing near to it. The colossal praying mantis held its pose, immovable. Presently it struck downward with lightning speed. There was a cry. The mantis rose erect again, its great arms holding something that stirred and struggled helplessly, and repented its unconsonanted outcry. The mantis ate it daintily as it struggled and screamed.

The humans did not watch this tragedy. The mantis would eat a man, of course. It had. The only creatures immune to its menace were ants, which for some reason it would not touch. But it was a mantis' custom after spotting its prey to wait immobile for the unlucky creature to come within its reach. It preferred to make its captures that way. Only if a thing fled did the mantis pursue with deadly ferocity. Even then it dined with monstrous deliberation as this one dined now. Still, mantises could be seen from a distance and hidden from. They were not the terror which had driven the humans even from their hiding-places.

It had been two weeks since the giant hunting-spider had come through a mountain pass into this valley to prey upon the life within it. It was gigantic even of its kind. It was deadliness beyond compare. The first human to see it froze in terror. It was disaster itself. Its legs spanned yards. Its fangs were needle-sharp and feet in length—and poisoned. Its eyes glittered with insatiable, insane blood-lust. Its coming was ten times more deadly to the unarmed folk than a Bengal tiger loose in the valley would have been.

It killed a man the very first day it was in the valley, leaving his sucked-dry carcass, and going on to destroy a rhinoceros-beetle and a cricket—whose deep-bass cries were horrible—and proceeded down the valley, leaving only death behind it. It had killed other men and women since. It had caught four children. But even that was not the worst. It carried worse, more deadly, more inevitable disaster with it.

Because, bumping and bouncing behind its abdomen as it moved, fastened to its body with cables of coarse and discolored silk, the hunting-spider dragged a burden which was its own ferocity many times multiplied. It dragged an egg-bag. The bag was larger than its body, four feet in diameter. The female spider would carry this burden—cherishing it—until the eggs hatched. Then there would be four to five hundred small monsters at large in the valley. And from the instant of their hatching they would be just such demoniac creatures as their parents. They would be small, to be sure. Their legs would span no more than a foot. Their bodies would be the size of a man's fist. But they could leap two yards, instantly they reached the open air, and their inch-long fangs would be no less envenomed, and their ferocity would be in madness, in insanity and in stark maniacal horror equal the great gray fiend which had begot them.

The eggs had hatched. Today—now—this morning—they were abroad. The little group of humans no longer hid in the mushroom-forests because the small hunting-spiders sought